**5. Conclusion**

Understanding the basic theory of CFD governing equations and numerical solutions is the key to developing CFD simulation codes as well as using CFD packages. Basically, all flows can be universally described by the continuity equation, component equation, momentum equation and energy equation, because fluid follows mass conservation, momentum conservation and energy conservation. With source terms, CFD applications were broadened to a wider field like chemical engineering, environmental engineering or thermal engineering. However, these equations are almost impossible to be solved analytically, thus we have to resort to the numerical method to get the approximate results. This involves using the finite difference method and finite volume method. The numerical methods offered a feasible way to get the solutions from the governing equations, which facilitated the analysis of complex phenomena associated with fluid flow, heat transfer and chemical reactions.
